If it is audio, it is better to splice both back together at a zero crossing point in the wave file. If you are ahead of the beat or behind you may want to cut it where the sound is what should be the start of the next wave form ahead of it at a relatively zero crossing point, the same with the second mark to cut out the section not wanted.
Then the rest of it and Snap to Grid is not needed, and you may find that not using that is better, otherwise, clicks and the wave sound probably will not sound right when finished.